Cardiopulmonary bypass surgery is being employed approximately 100,000 times per year in the U.S.A., and is associated with the development of subtle neurological changes that may become apparent months to years after surgery. In the future, blood carrying devices (pumps, oxygenators, valves, etc.) will be used more frequently and for longer periods of time. Protein denaturation during open heart surgery has been observed and confirmed, and may result in microaggregate formation and brain cell death or dysfunction, but little data is presently available on the contribution of the various components in heart-lung bypass to this event. Using a variety of chemical, biological and immunological probes we intend to define the specificity and course of changes in blood proteins in "in vivo" and "in vitro" experiments. Our long-term goal, of which this proposal is an important initial step, is to elaborate the consequences of protein denaturation on cell function, lipid transport, the microcirculation, the immune system, the reticuloendothelial system, and various enzymatic processes including the coagulation system. The information which we derive should facilitate development of new means for improving existing oxygen delivery systems and for monitoring bypass patients. In addition, identifying subtle changes in protein structure during short periods of exposure may help to avoid accumulative effects of chronic exposure to foreign surfaces.